| Re: open,/record - classification [message #717 is a reply to message #711] |
Mon, 16 November 1992 15:22  |
thompson
Messages: 584
Registered: August 1991
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Senior Member |
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In article <1992Nov16.152127.17585@newsserver.rrzn.uni-hannover.de>, knipp@ipi.uni-hannover.de writes...
> Hello there,
>
> We're runnig Pv~Wave Cl. 4.0 under SunOs 4.1.2
>
> There are 2 questions :
>
> a) Has anybody ever tried to open a device (p.e. a streamer-tape)
> for record-wise reading/writing ?. It should work under VMS, but we must do it
> under UNIX.
>
> b) Is there anybody who has programmed a land-use-classification in
> WAVE (or knows about an existing one) ?
>
> Thanks, KK
My experience is with IDL, not PV-WAVE, but this should still hold true. You
can open a tape device in Unix and do I/O using READU and WRITEU. At least I
was able to do this with an Exabyte tape drive on a Sun. You can also spawn
out to the OS to send commands such as
mt -f /dev/nrst1 fsf 1
or
mt -f /dev/nrst1 rewind
As I recalled, I just opened the device with the command
OPENU, UNIT, '/dev/nrst1'
I didn't use any keywords.
At one time I tried to write IDL procedures for Unix that imitated as closely
as possible the VMS tape utilities: TAPRD, TAPWRT, etc. I stopped working on
it, though, when I realized that there was no way to obtain the actual number
of bytes read in, as one could with the VMS routines. One place that was
crucial for us was in reading FITS tapes--we needed to be able to tell if the
tape was written using 2880 byte or 28800 byte records.
Bill Thompson
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